The Australian Manufacturers Workers Union (AMWU) says it will seek fresh assurances from Mitsubishi that it does not have a clandestine plan to shut its Australian operations.

Union to seek assurance from Mitsubishi

AMWU South Australian state secretary John Camillo said he had been told a leaked draft document titled "Project Phoenix" was not a policy of the car maker.

The report, outlining a secret plan for closing Mitsubishi's operations in Australia, was made public on ABC Television's 7.30 Report.

Mr Camillo said he first became aware of the leaked document when contacted by an ABC journalist several weeks ago, and this led him to contact senior management at Mitsubishi.

"The senior executive of Mitsubishi made it quite clear to us that, while they've done quite a few projects, there is no decision to close the Mitsubishi operation," Mr Camillo told AAP.

The car maker has 1,600 workers at its assembly plant, in Tonsley Park, in Adelaide's South, and Mr Camillo said these workers had received recent assurances from the company that their jobs were sound.

"If they (Mitsubishi) are dishonest, those workers will get to know that and the union will be extremely annoyed if that is the case," he said.

"If they try to hide those things, sooner or later it comes out in the open ... and it only makes it very very hard for Mitsubishi in Australia if that is the case."

Mr Camillo said he had called Mitsubishi following the program and was awaiting a return call.

The draft document, which was stamped confidential and dated September 6 this year, listed Mitsubishi Australia's chief executive Robert McEniry as the leader of Project Phoenix, the ABC reported.

It set out three possible dates for closure: February or October 2007 or March 2008.

It also said an announcement would be made just four months before the closure date, and the company would create the illusion of business as usual by continuing to place small orders for stock until one month before closure was announced.

According to the ABC, the document said ceasing local production was "inevitable" as sales of its locally made 380 sedan had failed to meet expectations and that Mitsubishi would remain in Australia only as an importer of vehicles.

The South Australian and federal governments would receive unofficial notice one month before the announcement, not the three to four months requested in case they leaked the closure plan to the media.

The unions would receive "no informal pre-notice at all".

Federal Treasurer Peter Costello said the government had been in touch with Mitsubishi about the report and had been told the company had no plan to cease production.

"I don't believe the contrary is true because Mitsubishi has given that information to the government," he told ABC TV.

He said the car company's acceptance of the government's multibillion dollar package, which continues until 2015, indicated that Mitsubishi regarded itself as having a long-term future manufacturing in Australia.

Mr Costello said he could not confirm the accuracy of the document, but the government would "very much" be concerned if the report was true.

"I'd be concerned a, about the industry, b, about the workers and c, that we have been assured to the contrary," he said.

"(But) you've got to be very careful with these things - it could be a false lead, it could be someone who's not in a position to make the decision."

Mr Camillo said any speculation about the closure of Mitsubishi's Australian operations came as a major blow to workers' morale at the Adelaide assembly plant.

"And it is alarming to see that part of that speculation is that there will be no consultation with the union if there is an announcement to close the Mitsubishi operation," he said.